Wireless-N a promising technology to connect controllers and I/Os
Letter from Cliff Whitehead and Paul Brooks of Rockwell Automation points to new possibilities with technology
In today's manufacturing sites, workers and automated machinery are becoming more mobile, and measurements and controls are being deployed in harder-to-reach locations. These changes are creating a compelling case for wireless networking as a part of the comprehensive control and information infrastructure in these sites. The good news is wireless technology is becoming suitable for deployment at an accelerating rate in a widening range of applications throughout the factory floor and as a complement to wired infrastructure. This creates a converged network infrastructure - wired and wireless - for both IT and manufacturing.
The industry is abuzz about current, albeit point-level, wireless networking solutions, while anticipating a future where wireless communications can be used throughout the factory and enterprise. These point-level solutions meet specific needs for a limited subset of applications. For example, extended enterprise zone wireless equipment on the factory floor increases worker mobility, but only allows access to automated equipment and processes.
Plants that deploy proprietary ISM radios meet mobile equipment needs, but prevent access to enterprise management information. To reach and measure previously inaccessible areas, some applications can use point-to-point links or application-specific solutions like WirelessHART. All of these wireless solutions fulfill niche applications, but do not offer a unified wireless approach that fully integrates the enterprise and the plant floor.
The technical breakthrough in Wi-Fi, the soon-to-be-ratified IEEE 802.11n (Wireless-N) standard, will make it possible to address a broad range of applications in manufacturing and production. Rockwell Automation and Cisco are testing this technology to determine its ability to meet the broad range of needs in industrial automation using standard, unmodified Wi-Fi. Wireless-N promises to change the industrial wireless market in the same way that full duplex 100MBps switches changed wired industrial Ethernet.
Like this milestone for wired Ethernet, Wireless-N will make I/O control and production practical for broad application.
Early testing by Rockwell Automation and Cisco indicates that solutions using Wireless-N technology provide the resiliency and deterministic, high-speed performance to meet the needs of mobile workers and of real-time communication between controllers and I/O.
Improvements to Wireless-N over previous technologies (802.11a/b/g) include significant performance increases, as well as the addition of features included in the N standard. These features include dual-frequency transmission, communication retries, better sensitivity and improved immunity to reflections (called MIMO - multiple input, multiple output - technology). Together, these performance increases will help improve the robustness of wireless without the need for proprietary solutions.
Wireless-N will provide the basic infrastructure fabric for broad application within a manufacturing or production facility. Wireless-N also will complement and easily integrate with long-haul communications using Internet Protocol (IP) over commercial radio technologies often used in SCADA applications, and with low-power, sensor mesh networks like WirelessHART or the emerging ISA100.11a standard.
As the industry moves to take advantage of this technology and the network convergence that it enables, manufacturers will have the ability to simplify communications architectures. This helps reduce capital as well as operation costs.
For example, a gantry crane application could use a single wireless network for several communications services. Services range from delivering pick lists based on customer orders via the MES system to interlocking safety signals between mobile and fixed equipment. With a single wireless infrastructure, mobile workers can access ERP tools from a regular laptop with a consistent experience from site to site, and office to plant floor. A single infrastructure will also help enable control capabilities on mobile and hard-to-reach equipment. These capabilities will help manufacturers reduce control system complexity and components as well as provide them with a window to real-time manufacturing information about the entire plant.
Likewise, a water treatment plant could combine wireless technologies to address several application needs. Over Wi-Fi and wireless mesh networks, a maintenance technician could remotely inspect the level transmitter on a clarification tank rotating arm. The wireless sensor eliminates the need for slip rings and flexible Ethernet cables, which helps increase uptime while reducing cost and number of components. The technician maintaining the instrument can simultaneously access the instrument, the asset management server and the internet through the facility's wireless network. Through these networks, the technician can check how the measurements and configuration compare with both the expected level indicated on the plant's data sheet as well as with the manufacturer's recommendations on the component data sheet. This hybrid wireless infrastructure helps provide the technician with the information needed to determine the most appropriate actions.
These are only a few of the many possible ways that manufacturers will deploy integrated wireless technologies for real-time information and control. However, business needs based on performance requirements and the application should drive a manufacturer's decision to use wireless. Usage should not be determined simply by a manufacturer's desire to implement wireless technology.
Regardless of application, proper design and deployment of the network infrastructure will remain critical to manufacturers' success. Finding the right expertise remains a challenge for many users, especially in the early years of wireless deployments. Generally, when it is practical to deploy wired networks, users will prefer this approach. However, in many applications, including mobile workers, mobile machinery and hard-to-reach locations, wireless technology will be preferred if - and only if - it meets the application's performance requirements.
Performance requirements should address reliability, quality of service and security needs. Reliability means more than whether the technology can deliver necessary information when it is needed. It means accommodating varying demands, which range from sending a few seconds of data once or twice a day to offering millisecond response rates for I/O control with a high-level quality of service. Performance requirements should also address data security needs, both for regulatory compliance and to protect commercial secrets. By controlling access, wireless networks can provide the same or a higher level of logical protection as the physical protection offered by a wired network. Robust data security also helps protect the wireless spectrum from unplanned radios and interference from unknown sources. By future-proofing their network infrastructure, manufacturers can accommodate planned extensions to the infrastructure. Today's technology can deliver all of these performance capabilities through best practice design methodologies.
Manufacturers will soon be able to use an integrated wireless network to meet a more diverse set of applications needs. Product suppliers continue to extend technology usage into new application space through research and innovative product developments. As this happens, manufacturers will implement an integrated networking solution - both wired and wireless - from the plant floor to the enterprise. Wireless-N will be an integral part of the unified, comprehensive networking infrastructure that manufacturers need to improve their overall business performance, agility and information access.
Cliff Whitehead, Manager, Strategic Applications
Paul Brooks, Business Development Manager